Reactive oxygen species (ROS) disrupt cell functioning by oxidatively denaturing lipids, proteins, sugars, nucleic acids and the like in the body. Normally the oxidation-antioxidation (redox) balance is strictly regulated in vivo, but when excess ROS are produced, the balance of oxidation-antioxidation factors tends towards oxidation. This condition is called “oxidative stress”, and is known as a causative or contributing factor in various diseases. In fact, it has become clear that a variety of diseases including Alzheimer's disease, Parkinson's disease and other intractable neurological conditions, arteriosclerosis, cerebral infarction, myocardial infarction, renal failure, diabetes, cancer and the like can occur when oxidative stress increases in the body. Thus, there is demand for the development of devices capable of effectively treating oxidative stress disorders.
In particular, it has become increasingly clear in recent years that oxidative stress caused by periodontal disease plays a significant role in systemic medical conditions. In such a specific area of the body, treatment with a low-molecular-weight or polymerized ROS scavenger is an option, but these ROS scavengers have poor therapeutic effects because they are easily eliminated from specific areas of the body such as periodontal pockets. To effectively treat diseases such as periodontal disease that affect specific areas of the body, and prevent these diseases from becoming systemic, a treatment must clear three hurdles: i) it must allow injection into the specific area, such as a periodontal pocket, ii) the injected drug must be retained long-term in the periodontal pocket or other specific area, and exhibit continuing effects, and iii) the treatment must be safe and not eliminate “good active oxygen,” which is involved in energy production.
In the past, the inventors have enclosed nitroxide radicals that catalytically remove active oxygen inside nanoparticles, and investigated these as intravenous or oral nanotherapies, which have been shown to be effective in cancer, ischemic disease and intestinal disease (see Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5). In particular, nanoparticles that are designed to break down and produce an antioxidative effect at disease sites with lowered pH, such as inflammation, cancer and the like, have proved highly safe and effective. Existing nanoparticles have proved useful in the critical role of safely transporting drugs in this way.
As discussed above, however, it is also necessary to provide means by which a therapy can be retained in an area of the body and produce a continuous effect while having practically no effect on other areas of the body.